1. Field of the Invention
The present invention relates to a method of manufacturing a liquid ejection head such as an ink jet recording head, and a liquid ejection head formed by the method.
2. Description of the Related Art
Japanese Patent Publication No. H06-45242 describes a method of producing an ink jet recording head which is one of liquid ejection heads. First, an ink flow path pattern is formed with a soluble resin on a substrate having formed thereon energy generating elements. Next, a covering resin layer including a cationically polymerizable resin and a photocationic polymerization initiator is formed on the ink flow path pattern, and ink ejection orifices are formed above the energy generating elements by photolithography. Finally, the soluble resin is dissolved and the covering resin layer is then cured to form an ink flow path member.
On the other hand, as described in Japanese Patent Application Laid-Open No. H05-127369, it has been known that a material which functions as a base such as an amine is added to an acid generated from a photocationic polymerization initiator so as to obtain a patterned shape having good dimensional controllability with a chemical amplification type resist. This material renders an acid concentration distribution in a mask edge steep to enhance the dimensional controllability.
In order to realize high-quality printing and obtain a stable printing effect constantly in an ink jet printer, it is desired that ink meniscus be constantly formed at a given position in an ink ejection orifice.
Herein, FIGS. 1A to 1C are cross-sectional views of an ink ejection orifice, illustrating meniscus 4a of ink 4. In the case where an ink ejection orifice edge is sharp as indicated by reference numeral 3a in FIG. 1A, the meniscus 4a of the ink 4 can be constantly formed at a given position. On the other hand, in the case where the ink ejection orifice edge is round as indicated by 3b in FIGS. 1B and 1C, meniscus of ink may not be formed at a given position in the ink ejection orifice.
In the case of forming an ink ejection orifice by photolithography, in order to cure an ink flow path member 1 up to a bottom portion thereof, the exposure amount of a surface of the ink flow path member 1 (ink ejection orifice surface 2a) on which an ejection orifice is to be formed is larger than that of the bottom portion. Specifically, the amount of an acid generated from a photocationic polymerization initiator on the ink ejection orifice surface 2a is larger than that of the bottom portion of the ink flow path member 1, and a curing reaction proceeds rapidly in the vicinity of the ink ejection orifice surface 2a. Consequently, the edge shape of the ink ejection orifice may become round. That state tends to become more conspicuous as the thickness of the ink flow path member 1 increases.
Here, the edge shape of the ink ejection orifice can be prevented from becoming round by adding a basic material such as amine to the ink flow path member as described above to deactivate an acid generated in the vicinity of the ink ejection orifice surface. However, this effect applies to only the case where the thickness of the ink flow path member is small. The basic material is present uniformly in the ink flow path member, and hence, in the case where the thickness of the ink flow path member increases, the exposure amount of the ink ejection orifice surface for curing the ink flow path member up to the bottom portion thereof increases further. Therefore, the acid generated in the vicinity of the ink ejection orifice surface is present in a large amount without being deactivated completely with a basic material, with the result that the curing reaction proceeds rapidly in the vicinity of the ink ejection orifice surface, and the edge shape of the ink ejection orifice ends up becoming round.
In view of the foregoing, it is an object of the present invention to provide a liquid ejection head, the edge shape of a liquid ejection orifice of which is sharp even in the case where the thickness of a liquid flow path member increases, and which enables high-quality printing, and a method of manufacturing the liquid ejection head.